Fluorochemicals are compounds in which some or all the carbon-hydrogen bonds are each replaced by carbon-fluorine bonds. These carbon-fluorine bonds are some of the strongest in nature and contribute to the unique stability of fluorochemicals.
Perfluorooctanoic acid (PFOA), also known as C8, is an artificial acid that has many industrial uses. PFOA and related substances are synthetic fluorochemicals useful for processing agents for manufacturing fluoropolymers and do not naturally occur in nature. Fluoropolymers with their many beneficial attributes are employed in widespread industrial settings including the textile, aerospace, electrical, and building construction industries.
PFOA designates the acid itself, and is also commonly used to refer to salts thereof such as ammonium perfluorooctanoate. One of the most common uses of PFOA is for processing polytetrafluoroethylene PTFE. PFOA is also a byproduct of the telomerization process. The telomerization process produces perfluorinated alcohol, which is commonly used in many household surface finishes and indirect contact applications in flexible food packaging. The PFOA byproduct is also in the fabrication of water- and stain-resistant clothes and other materials; aqueous film forming foam (AFFF); and in food packaging. Fluorotelomeric compounds are used in food packaging to make them resistant to grease; however, these fluorotelomeric compounds are metabolized PFOA. These compounds have been used in microwave popcorn bags, fast food and candy wrappers, and pizza box liners. In particular, microwave popcorn bags have the high fluorotelomer content, and the high cooling temperatures increase the migration of these chemicals into the popcorn oil. It is estimated that microwave popcorn accounts for more than 20% of the average PFOA levels measured in American residents. Its elimination half-life is reported as being 4 years.
Durability of PFOA prevents it from breaking down once in the environment, leading to widespread buildup and bioaccumulation in food chains. Traces of PFOA-family chemicals can now be found in the blood of nearly all Americans and in the environment worldwide and environmental regulatory agencies have become increasingly concerned about possible adverse health effects in animals and humans. Accordingly, information regarding cellular and or tissue distribution and metabolism PFOA and related substances in humans, animals, birds, fish, insects, and plants would be instrumental in evaluating concerns.
The elimination, tissue distribution, and metabolism of PFOA were previously examined in male and female rats (Vanden Heuvel J. P. et al., J. Biochem. Toxicol. 1991, 6(2): 83-92) wherein PFOA was labeled with carbon-14. Female rats were found to have eliminated PFOA-derived radioactivity rapidly in the urine. In the same period, male rats were observed to have eliminated only 6% of the administered carbon-14 in the urine. Analysis of PFOA-derived carbon-14 in tissues showed that the liver and plasma of male rats and the liver, plasma, and kidney of female rats were the primary tissues of distribution. Due to inherent detection limitations, this reference, however, fails to provide visualized imaging information regarding distribution and metabolism of PFOA.
U.S. Pat. No. 6,445,449 describes a method and an apparatus for determining the presence, in a sample, of compounds having carbon-halogen bonds and, in particular, carbon-fluorine bonds. The method uses pulsed laser Raman spectroscopy to detect carbon-halogen bonds, using an effect of inelastic scattering of light. The method does not identify a halocarbon compound, but instead the presence of a carbon-halogen bond is determined, using the carbon-halogen bond as a chemical tracer for the halocarbon. The method is useful for analysis of fluoroorganic compounds at ppm-ppb level for pharmaceutical, biological, medical and biomedical applications. This method, however, does not address how a compound having the carbon-halogen bond would distribute within a subject, much less the distribution information in a visualized imaging format.
Thus, there exists a need for a composition and a process for concurrently and visually accessing both the tissue distribution and cellular metabolism of PFOA and related substances in a living subject or a biological sample thereof using visualizing imaging tools such as PET or SPECT.